All-organic actuator fabricated with single wall carbon nanotube electrodes

Compliant electrodes to replace conventional metal electrodes have been required for many actuators to relieve the constraint on the electroactive layer. Many conducting polymers have been proposed for the alternative electrodes, but they still have a problem of poor thermal stability. This article reports a novel all- organic actuator with single wall carbon nanotube (SWCNT) films as an alternative electrode. The SWCNT film was obtained by filtering a SWCNT solution through an anodized alumina membrane. The conductivity of the SWCNT film was about 280 S/cm. The performance of the SWCNT film electrode was characterized by measuring the dielectric properties of NASA Langley Research Center – Electroactive Polymer (LaRC-EAP) sandwiched by the SWCNT electrodes over a broad range of temperature (from 25 to 280 °C) and frequency (from 1 kHz to 1 MHz). The all-organic actuator with the SWCNT electrodes showed a larger electric field-induced strain than that with metal electrodes, under identical measurement conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2532–2538, 2008     

悬线式物镜力矩器动态特性的仿真实验研究

悬线式物镜力矩器是目前光学头系统中使用最为广泛的力矩器,其动态特性直接决定了光学头的读写性能。基于ANSYS参数化设计语言(APDL)建立了悬线式光学头物镜力矩器的仿真设计平台。通过仿真平台进行了力矩器一阶共振频率和峰值、二阶共振频率和峰值、扭转共振频率、静态灵敏度、动态灵敏度和相位等动态特性参数的仿真实验,仿真计算的结果与实际测量的结果相比,最大相对误差为4.2%。该仿真平台对于二维乃至三维悬线式物镜力矩器的设计和评价都具有重要的指导意义。     

Epoxy-based electroactive polymer gels

We describe a new type of electroactive polymer gel. In contrast to cross-linked polyacrylates, this system is based on triepoxides cross-linked with polyfunctional amines. The stoichiometry is selected to form a cross-linked gel with excess amino hydrogens. In acid solutions these become cationic and the ionic interactions cause the gel to swell. We describe the mechanical properties of the gels, their response to changes in pH and to electrical activation. The response time is in rough agreement with what would be expected for a diffusional process through a gel of this size (about 100 μm). Samples of smaller dimensions would be expected to respond more rapidly.     

Sliding mode control of a “Soft” 2-DOF Planar Pneumatic Manipulator

This paper presents a sliding mode controller for a “Soft” 2-DOF Planar Pneumatic Manipulator actuated by pleated pneumatic artificial muscle actuators. Since actuator dynamics is not negligible, an approximate model for pressure dynamics was taken into account, which made it necessary to perform full input-output feedback linearization in order to design a sliding mode controller. The design of the controller is presented in detail, and experimental results obtained by implementing the controller are discussed Published in Prikladnaya Mekhanika, Vol. 44, No. 10, pp. 135–144, October 2008.     

自适应超静定桁架强度控制能力的提高

利用作动器的调节功能和超静定桁架的内力耦合特性,提高了自适应超静定桁架结构的承载能力,获得了更加合理的结构工作状态,有效地解决了文[8]中当作动器刚度较小时调控能力受限的问题。计算结果比文[8]模型的结果更令人满意。     

Ionic Polymer‐Metal Composite Actuators Employing Radiation‐Grafted Fluoropolymers as Ion‐Exchange Membranes

Summary: To develop ionic polymer‐metal composites (IPMC) with improved performance, three new ion‐exchange membranes were prepared and employed in IPMC construction. The membranes were prepared by radiation‐grafting of polystyrene sulfonic acid onto three fluoropolymers; poly(vinylidenefluoride‐co‐hexafluoropropylene), poly(ethylene‐co‐tetrafluoroethylene), and poly(tetrafluoroethylene‐co‐hexafluoropropylene). The bending displacements of the IPMCs constructed with these membranes were at least several times larger than that of Nafion IPMC of similar thickness without straightening‐back. The larger displacement was considered to be due to the higher concentration of ionic groups and consequent larger ion‐exchange capacity.

Actuation of (a) Nafion IPMC and (b) IPMC prepared in this study.     

Control of an axially moving viscoelastic Kirchhoff string

The control problem of axially moving strings occurs in a large class of mechanical systems. In addition to the longitudinal displacement, the strings are subject to undesirable transversal vibrations. In this work, in order to suppress these vibrations, we consider a control by a hydraulic touch-roll actuator at the right boundary. We prove uniform stability of the system using a viscoelastic material and an appropriate boundary control force applied to the touch rolls of the actuator. The features of the present work are: taking into account the mass flow entering in and out at the boundaries due to the axial movement of the string and overcoming the difficulty raised by the Kirchhoff coefficient which does not allow us to profit from the dissipativity of the system (as in the existing works so far). We shall make use of an inequality which is new in this theory.     

Deformation of cross-linked liquid crystal polymers by light – from ultraviolet to visible and infrared

ABSTRACT

Collecting and amplifying the nanoscopic molecular motions into macroscopic deformation is the unique property of cross-linked liquid crystal polymers (CLCPs). These materials can directly transfer input light energy into mechanical work when combined with photochromophores, thus fascinating many scientists. This article reviews the macroscopic and microscopic deformation of photoresponsive azobenzene-containing CLCPs and analyses the influence of mesogen alignment and chemical structure on shape change behaviour. We highlight some new methods to trigger the deformation by visible and infrared light instead of ultraviolet one, such as chemical modification of azobenzene and addition of upconversion materials.     

压电堆叠作动器的对称性求解

研究了压电堆叠作动器的对称性,并给出了系统存在的守恒量和对称性解.以轴向运动的压电堆叠作动器为研究对象,根据其结构特点,选取位移和磁链作为广义坐标,运用能量方法,建立了压电堆叠作动器的Lagrange(拉格朗日)方程.引入位移和磁链广义坐标的无限小群变换,分别研究了压电堆叠作动器的Noether对称性和Lie对称性,给出了广义Noether恒等式、广义Killing方程、广义Noether定理和Lie定理,计算了压电堆叠作动器存在的Noether对称性和Lie对称性的生成元,并给出了相应系统存在的守恒量.最后,利用得到的守恒量,给出了压电堆叠作动器对称性解,并计算了在控制电压变化的情况下位移和速度的动态响应曲线.     

Numerical Investigation and Feasibility Study of a PZT-driven Micro-valve Pulsed-jet Actuator

A micro-valve pulsed-jet vortex-generator driven by piezoelectric actuation was successfully modelled numerically to determine the feasibility of such a design. This includes: modelling the dynamic motion of a unimorph cantilever and the fluid-structure interaction occurring between the unimorph and the fluid flowing over such a structure; the unsteady developing channel flow that would occur through the outlet orifice was also modelled. The initial design was found to have several fundamental flaws that were shown to be easily remedied. The fluid-structure interaction was found to have a strong effect on the motion of the piezoelectric beam and therefore the performance of the pulsed-jet actuator. The response time of the actuator was found to be governed by the micro-valve opening rather than the time taken to establish the jet. However, the resistance of the pulsed-jet actuator was shown to be governed by the outlet orifice; it was an order of magnitude larger than the resistance of the micro-valve.